This invention relates to gas turbine engines and particularly for an automatic stall recovery system thereof.
As is well known in the gas turbine industry, stall of axial flow compressor blades has long plagued the industry. Stall or surge is that phenomenon where flow separation adjacent the compressor blades is manifested causing a severe pressure reversal or pulsation. This pulsation, if allowed to persist not only impairs engine performance but can cause severe injury to the engine.
Although it is typical to provide in the fuel control optimum scheduling that attempts to operate the engine below the surge line, under adverse aircraft/engine transient operating conditions, this is sometimes not sufficient. Either the schedule is not accurate or errors either in the sensors or due to distorted signals for example so that as with a consequence this scheduling is not adequate. Hence, there has been attempts in the industry to detect surge, or rather, detect imminent surge, since the phenomenon of surge can occur so fast that it may be catastrophic. Also, because of engine peculiarities, surge controls for one engine model may not be satisfactory for another. As an example, the time response for one given engine may be satisfactory to stop or correct for the surge once detected but in another, it may be too slow.
This invention contemplates obviating the problems noted above by providing an automatic stall recovery system. When the turbine inlet temperature becomes disproportionately high compared to rotor speed then the fuel flow is automatically shutoff. At a predetermined compressor condition, namely, when the compressor discharge pressure reaches a predetermined value, the ignition system is actuated to commence restarting the engine.